1. Field of the Invention
The present invention relates to an exposure control device for a camera, and more particularly to such a device capable of controlling exposure a flash photography.
2. Description of the Prior Art
Day light flash photographing under rear light condition has been known by Japanese laid open Patent Application 59-123825, wherein an exposure value for controlling shutter and diaphragm is decided corresponding to ambient light in the peripheral area of a photographic field, then exposure is made for the main object by means of controlling flash light amount under the ambient light. According to the above method, since the main object and the peripheral area are evenly exposed with the respective appropriate exposure values, the finished photography looks like that taken under a normal light condition with the rear light effect lost, which would be contrary to the camera man's intention if he is to take the photography with the effect of the rear light.
Moreover, in the flash photographing, in case of using so called a TTL camera in which the light measurement is carried out using the light incident to the lens of the camera, when the main object is located in a peripheral area of the finder, reflection light from the central area at which a background is located is few. Therefore, if the flash is automatically controlled by integrating reflection light under such condition as mentioned above, there tends to occur an over exposure for the main object located in the peripheral area. To the contrary, in case a sub object is located in the central portion of the finder with a distance closer to the camera than the main object, a large amount of reflection light enters in the camera and the flash control is decided corresponding to the large amount of the light, whereby there occurs under exposure for the main object located in the peripheral area.
In the prior art, it has been known to control the exposure in flash photography in accordance with information of the object distance obtainable through an automatic focus adjustment to the main object located in the central portion of the object field. According to such a prior art, the information of object distance of the main object is fixed and maintained once the automatic-focus adjustment has been completed even if the main object is shifted afterward to the peripheral portion of the object field for actual exposure. However, because of the uneven illumination characteristic of the flash, an under exposure to the main object in the peripheral portion of the object field would result in comparison with a case in which the main object is located in the central portion of the object field. This can not be compensated since the object distance information, which is fixed once the automatic focus adjustment has been completed, has no information of whether the main object is shifted to the peripheral portion or maintained in the central portion upon actual exposure.